1. Field of the Invention
The present invention relates to a system and method for measuring a position of a moving object such as a vehicle with a hybrid navigation apparatus, the hybrid navigation apparatus being the combination of an electromagnetic-wave type position measuring apparatus and an integration calculation position measuring apparatus.
2. Description of the Prior Art
A Japanese Patent Application First Publication (Tokkai) sho No. 60-135817 exemplifies a conventional hybrid-type position measuring system entitled to a running guide apparatus for an automotive vehicle.
In the conventional hybrid position measuring system disclosed in the above-identified Japanese Patent Application Publication, an electromagnetic wave navigation apparatus constituted by the electromagnetic wave position measuring apparatus and inferential navigation apparatus constituted by the integration calculation position measuring apparatus are complementarily combined in the position measuring system and when a reception state of the electromagnetic wave from a GPS (Global Positioning System) geostationary satellite becomes worse (low signal-to-noise ratio), the electromagnetic wave navigation apparatus is switched to the inferential navigation apparatus to continuously make an accurate measurement of a position of the vehicle in an area of the earth.
However, the conventional hybrid position measuring system disclosed in the above-identified Japanese Patent Application Publication has a problem that measurement results of the electromagnetic wave position measuring apparatus are used as reference positions of the integration calculation position measuring apparatus so that each of the measurement results of the electromagnetic wave position measuring apparatus is directly set to the reference position on the basis of which the integration calculation position measuring apparatus measures the position of the vehicle even if large errors are included in the measurement results of the electromagnetic wave position measuring apparatus. Consequently, since an erroneous result of measurement is outputted or set to the reference position, a reliable measurement result of the present position of the vehicle cannot always be achieved.